This invention relates to facsimile systems comprising a transmitter, a receiver and a communications network such as telephone lines therebetween. The transmitter employs a scanning or reading element which reads the information content of an original document. The original document is moved relative to the reading means such that successive paths are scanned whereupon the output of the scanning element is fed to a device such as a photodetector which converts the variations in light intensity received by the scanning element due to variations in the reflectivity or transmissivity of the scanned copy to electrical signals. These electrical signal then convey information concerning the radiation absorption, emission or reflection of the scanned document. The electrical information-bearing signals are then transmitted to a receiving unit over suitable means such as a telephone network and the receiving unit converts the electrical information-bearing signals from the transmitting unit to marks or images on a receiving copy medium so that the received copy is a reasonable facsimile of the original scanned document.
In commercially available facsimile systems, rather complex lens-mirror optical systems are utilized in the scanning of a document. These lens-mirror optical systems which are capable of achieving the necessary level of resolution, are extremely expensive and constitute a considerable portion of the overall cost of a rather expensive transceiver.
The use of fiber optics in the optical scanning system of facsimile transceivers has also been suggested. In U.S. Pat. No. 3,553,366 -- Brouwer, a flexible fiber optic is utilized for optically scanning a document in combination with a lens which separates the document being scanned from the reading fiber optic.
In U.S. Pat. No. 3,588,514 -- Simpkins, a reading fiber optic which is surrounded by a plurality of illuminating fiber optics is located in the recess of a block which rides on the surface of the document being scanned and thereby places the reading fiber optic in direct optical communication with the document. A tube encloses the reading fiber optic as well as the illuminating fiber optics which surround the reading fiber optic to prevent wear and the accumulation of foreign matter and debris on the end of the tube. Although the depth of the recess is indicated as 0.0005 to 0.001 inches and the tube enclosing the fiber optics is indicated as flush with the base of the recess, there is no indication as to the spacing between the end of the reading fiber optic and the document which will have a critical effect on the resolution which can be achieved. There is also no indication as to the relationship between the diameter of the reading fiber optic and this spacing.
U.S. Pat. Nos. 3,201,512 -- Mason et al and 3,448,207 -- Green et al also disclose or suggest the use of fiber optics in a facsimile system. Neither patent discloses or discusses the nature of the spacing between the ends of the fiber optics and the document being scanned.
In addition to failing to teach the nature of the critical spacing which must be maintained to optimize the resolution of a facsimile system and properly illuminate the area being scanned, the prior art also fails to disclose a means by which the end of the fiber optic may be maintained clear of debris. Although the Simpkins patent does disclose the use of a recess which is provided, ostensibly for this purpose, it has been found that a recess alone can actually compound the problems of maintaining the end of a fiber optic free of debris. Since the recess itself serves to collect debris, the debris will cover the end of the reading fiber optic as well as the illuminating fiber optics if the ends of those fiber optics are flush with or below the base of the recess.
The prior art also fails to disclose a means by which the spacing between the end of the fiber optic and the document being scanned can be maintained without undesirable fluctuations when a discontinuity in the document thickness passes the fiber optic. In the case of the Simpkins patent, the block containing the fiber optic rides on the document being scanned. As a result, any discontinuity in the document thickness will create a bouncing between the block and the document which will in turn affect the spacing of the document from the end of the reading fiber optic.